Previously disclosed metering devices for systems with varying flows are often cumbersome and expensive if they are executed in such a way that they can cope with precise metering within a wide flow range. This normally calls for a valve system with several moving parts, with bearing points for all of these.
One area of application for such metering devices, for example, is sprinkler systems for fire-fighting by means of foam. It is very important in such systems for the proportion of foam to be capable of being retained at an exact percentage value, e.g. from ca. 50 l/min to ca. 7000 l/min. It is difficult to achieve the desired accuracy, in particular at low flows. One example of an application for which it has proved difficult to find a solution is when the foam consists of so-called ARC (Alcohol Resistant Concentrate) foam, which belongs to the category of non-Newtonian liquids with varying viscosity and partially thixotropic characteristics.
The large flow register is explained by the requirement to cover the largest possible surfaces with one and the same system, in conjunction with which the small flow occurs when an individual section of the system is triggered, and the rest of the flow quantity occurs at the full capacity of the sprinkler system.